Turbojet with protection means for a fuel injection device, an injection device and a protective plate for the turbojet
The turbojet of the invention includes a combustion chamber, a channel for heating the gas stream, where the heating channel includes at least one device for injection of fuel into the gas stream, which includes an open chamber, with a U-shaped section, having at least one wall within which extend fuel-injection means, which inject the fuel in at least one direction. It is characterised by the fact that a cooling jacket is provided in the chamber, alongside the wall forming the base of its U-section, and the fuel injection device includes protection means interposed between the fuel-injection means and the wall, in a fuel-injection direction. Thus, as a result of the invention, the fuel injection device, which is bathed in a very hot environment, is protected against thermal shocks due to the projection of colder fuel onto its walls, and its life expectancy is therefore increased.
Latest SNECMA Patents:
The invention concerns a turbojet which has a channel for heating of the primary gas flow, with a fuel injection device and protection means for the fuel injection device. The invention also concerns a fuel injection device and a protective plate for the said turbojet.
Turbojets which are described as “post combustion” generally include, from upstream to downstream in the direction of flow of the gases, one or more compressor stages, a combustion chamber, one or more turbine stages, a heating or post combustion channel, and an exhaust nozzle. The primary gas flow, downstream of the turbine stages, allows a fresh combustion, as a result of the oxygen still present within it, in the heating channel before expanding in the exhaust nozzle.
At the entrance of the heating channel, flame holder arms extend radially into the gas stream. They are of U-shaped section, the branches of the U being orientated in the downstream direction, and have within them a fuel injector projecting the latter into the stream of gas in the downstream direction. The fuel is ignited and the flames are attached to the walls of the arms because the shape of the arm section creates a zone with a lower pressure. A flame holder ring, concentric with the housing of the heating channel, can also be provided in the gas jet of the primary stream. This functions on the same principle.
The primary stream is at a temperature of about 950° C. The walls of the flame holder arms, although cooled by a jacket fed with air from the secondary air stream at 200 or 250° C., are at a temperature of around 800 to 850° C., in particular at their trailing edge, while the flames attached to the arms are at a temperature of 1700° C. The fuel is projected at a temperature of about 100° C., or more precisely between 50 and 150° C., against the walls of the arm at 850° C.
The thermal gradients resulting from this impact are very large, and lead to deformation of the arms, in particular at their trailing edge. Because of this, their life expectancy is reduced, this being all the more serious since the arms are generally made from castings in Cobalt-based alloys, and are difficult to replace. The maintenance costs are therefore very high.
In the case of an annular injection device with two walls forming a chamber that is open upstream and downstream, document U.S. Pat. No. 5,179,832 proposes, a protective plate adjacent to the external wall, against which the fuel is projected. The fuel is projected by a fuel injector tube standing away from the inner end of the upstream jet of the chamber. Such protection is not satisfactory however, in the case of a chamber that is closed on the upstream side.
This present invention aims to overcome these drawbacks.
To this end, the invention concerns a turbojet that includes a channel for heating of the gas stream, where the heating channel includes at least one device for the injection of fuel into the gas stream, which includes an open chamber with a U-shaped section and with at least one wall, and within which extend of fuel-injection means which inject the fuel in at least one direction, characterised by the fact that a cooling jacket is provided in the chamber, alongside the wall forming the base of its U-section, and the fuel injection device includes protection means interposed between the fuel-injection means and the wall, in a fuel-injection direction.
Preferably, the protection means include at least one plate.
Again preferably, the injection device comes in the form of a radial arm.
Advantageously in this case, the protection means extend along the full radial height of the arm.
Preferably again, the fuel-injection means include at least one tube, supplied with fuel and including fuel-injection orifices.
Advantageously, the fuel injection device also includes a protective screen, placed in the opening of the chamber, the protection means being positioned between a wall of the chamber and the protective screen.
Depending on the form of implementation, the fuel-injection means are placed between the walls forming the branches of the U-section of the chamber.
Preferably in this case, a plate is placed more or less parallel to each of the walls of the chamber forming the branches of its U-section.
Depending on the form of implementation, each plate is attached to the wall to which it is more or less parallel.
According to another form of implementation, each plate is attached to the cooling jacket.
According to yet another form of implementation, the plate includes a U-section, and a radial recess in the central part of the wall forming the base of its U-section, which is slid onto a part forming a slide, attached to the cooling jacket.
The invention also concerns a fuel injection device for the above turbojet.
The invention again concerns a protective plate for a fuel injection device for the above turbojet.
The invention will be better understood with the aid of the following description of the preferred form of implementation of the turbojet of the invention, with reference to the appended drawings, in which:
With reference to
At the entrance of the heating channel 5, fuel-injector arms 7, attached to the external housing 5″ and to the internal jacket 5′ of the heating channel 5, extend radially. The function of the injectors is to vaporise fuel in the direction of flame holder arms 8, located downstream in the heating channel 5.
With reference to
Close to the internal jacket 5′ of the heating channel 5, in the heating channel of the primary stream 5, the flame holder arms 8 support a flame holder ring 9. This ring 9 is composed of a multiplicity of portions of ring 9′, nine in number, which extend, concentrically to the housings 5′, 5″ of the heating channel 5, between two successive flame holder arms 8.
With reference to
The flame holder arms 8 extend radially, inclined in the downstream direction, from their base attached to the external housing 5″ of the heating channel 5, in relation to the perpendicular to the axis 1′ of the turbojet 1 contained in the axial plane of the arm 8. A flame holder arm 8 includes an open chamber, delimited by walls 8′—which can be replaced in a similar manner by a continuous wall 8′—in which its various elements are contained. The flame holder arm includes a radial cooling jacket 8a, extending over all of the radial height of the arm 8, parallel to which extends, downstream, a fuel injector tube 8b, supplied with fuel from the exterior of the external housing 5″ and including jets for projection of the fuel.
The simplified operation of the turbojet is as follows. Fuel is vaporised by the fuel injector tubes 7b of the fuel-injector arms 7 and by the fuel injector tubes 8b of the flame holder arms 8. As a result of the residual oxygen in the primary gas flow, and also due to a contribution of air from the secondary stream, this fuel undergoes combustion. This combustion occurs at the flame holder arms 8, the shape of which causes the attraction of the flames by the said arms 8. This combustion, known as post combustion or re-heating, provides additional impulsion to the turbojet. This process of post combustion is well known to the professional engineer and will therefore not be treated in greater detail here. The gas then expands in the heating channel 5 and in the exhaust nozzle 6 before of being ejected out of the turbojet 1.
With reference to
A protective plate 8d extends between the walls of the protective screen 8c and the walls 8′ of the arm 8. Its function is to prevent a direct impact of the fuel onto the walls 8′ of the arm 8, the drawbacks of which have been presented above. In the form of implementation of
Thus the fuel, indicated by dashed lines 10, is sprayed from the fuel injector tube 8d onto the protective plates 8d, before being ejected, between the said plates 8d and the protective screen 8c, beyond the arm 8, where it is ignited.
In
The protective screen 8c is fixed to the protective plate 8d at the portions of its walls that correspond to the branches of its U-section, by the same securing pins 11. Such a portion of wall generally takes the form of a plate, including indentations 13 in which holes are drilled for passage of the securing pins 12. Thus, the screen 8c is pinned onto the plate 8d at the location of the indentations 13, while the major part of its surface is held away from the plate 8d, so as to leave a space for passage of the fuel 10.
The securing pins 11 are not specified, and will be chosen by the engineer concerned.
As a result of the protective plates 8d, the fuel 10 projected by the tube 8b does not make contact with the walls 8′ of the arm 8, the temperature of which is very high, and so prevents them from being subjected to excessive temperature gradients. It is projected onto the protective plates 8d, which are located inside the space defined by the walls 8′ of the arm 8, and are at a lower temperature, due in particular to the cooling provided by the jacket 8a. Their temperature is typically 600 to 650° C., instead of 850° C. for the walls 8′ of the arm 8. The thermal gradient to which they are subjected is therefore less severe. The plates 8d can be composed of any ad-hoc material, such as metal, ceramics or ceramic matrix components (CMC).
The plates 8d thus protect the walls 8′ of the arm 8, since they are placed between the tube 8b and the walls 8′ of the arm, in the fuel-injection direction. They undergo deformations, but once deformed, they are easily to replace, or at least easier than the walls 8′ of the arm 8, resulting in lower maintenance costs than for structures of earlier design.
Other methods of attachment and other shapes of the protective plates 8d can also be envisaged.
With reference to
With reference to
In order to increase its life expectancy, the protective plate 8d, in its downstream area close to the trailing edge of the arm 8, can be shaped otherwise than a simple plate, irrespective of its overall shape.
With reference to
According to another form of implementation, the walls of the plate 8d can present, in their downstream end portion, or even over all of their wall that is more or less parallel to a wall 8′ of the arm 8, a section, seen in transverse section in relation to the general plane of the wall, of corrugated shape, which allows the deformations associated with the thermal gradients to be absorbed. In fact, this type of corrugation is generally the result of the deformations, and being able to do it in advance allows one to pre-stress the plate 8d to some degree.
The invention has been presented in relation to a fuel injection device in the primary gas flow which is a radial arm, but it goes without saying that the invention applies to all types of fuel injection device in the primary gas flow, and a ring in particular.
Claims
1. A turbojet including an afterburner channel for heating of a gas stream, at least one injection device for injecting fuel into the gas stream, the injection device comprising:
- an open chamber, with a U-shaped section, having at least one wall and within which extends a fuel injector that injects fuel in at least one direction,
- a cooling jacket in the open chamber, alongside the base of the U-shaped section,
- a protection device interposed between the fuel injector and the wall, in a fuel-injection direction so as to prevent a direct impact of the fuel from said fuel injector onto said wall, and
- a protective screen positioned downstream of said fuel injector and configured to protect the fuel injector tube from ignited fuel,
- wherein said protection device is located between said protective screen and said wall, and wherein said protection device and said protective screen are configured and positioned with respect to each other so as to define channels between said protection device and said protective screen for the fuel to be ejected through said channels and beyond said wall of the open chamber before being ignited.
2. A turbojet in accordance with claim 1, wherein the protection device includes at least one plate.
3. A turbojet in accordance with claim 1, wherein the injection device forms a radial arm.
4. A turbojet in accordance with claim 3, wherein the protection device extends over all of the radial height of the radial arm.
5. A turbojet in accordance with claim 1, wherein the fuel injector includes at least one tube, supplied with the fuel and including fuel-injection jets.
6. A turbojet in accordance with claim 1, wherein the fuel injector is placed between walls forming the branches of the U-shaped section.
7. A turbojet in accordance with claim 1, wherein said U-shaped section includes a first branch and a second branch, and said protection device includes a first plate substantially parallel to said first branch and a second plate substantially parallel to said second branch.
8. A turbojet in accordance with claim 7, wherein each plate is attached to a wall to which the plate is substantially parallel.
9. A turbojet in accordance with claim 7, wherein each plate is attached to the cooling jacket.
10. A turbojet in accordance with claim 2, wherein the plate includes a U-shaped section and a radial recess in a central part of the base of the U-shaped section of the plate, which is slid onto a part forming a slide, attached to the cooling jacket.
11. A turbojet in accordance with claim 2, wherein the plate includes slots.
12. A turbojet in accordance with claim 2, wherein the plate includes a portion of corrugated wall.
13. A turbojet in accordance with claim 1, wherein the injection device forms a ring.
14. A turbojet in accordance with claim 1, wherein said U-shaped section includes a first branch and a second branch, and said protection device includes a first plate and a second plate, wherein said first plate is between said fuel injector and said first branch so as to prevent direct impact of the fuel from said fuel injector onto said first branch, and wherein said second plate is between said fuel injector and said second branch so as to prevent direct impact of the fuel from said fuel injector onto said second branch.
15. A turbojet in accordance with claim 14, wherein said first plate is substantially parallel to said first branch, and said second plate is substantially parallel to said second branch.
16. A turbojet in accordance with claim 14, comprising a plurality of flame holder arms, each flame holder arm being configured as said injection device, wherein said flame holder arms are arranged around the circumference of said heating channel and extend radially inside said heating channel from a heating channel jacket.
17. A turbojet in accordance with claim 16, further comprising a plurality of fuel-injector arms, each fuel-injector arm having a fuel injector, wherein said fuel-injector arms are arranged around the circumference of said heating channel and extend radially inside said heating channel from said heating channel jacket, wherein said fuel-injector arms are positioned upstream relative to said flame holder arms.
18. A turbojet in accordance with claim 17, wherein said flame holder arms are angularly offset in relation to said fuel-injector arms so that, when viewed face on, each fuel injector arm is located between two adjacent flame holder arms and equidistant from each of said two adjacent flame holder arms.
19. A turbojet in accordance with claim 1, wherein the protective screen is U-shaped with arms substantially parallel to said protection device.
20. A turbojet in accordance with claim 1, wherein said protection device includes two distinct plates separated from each other, each plate being between said wall and said protective screen.
21. A turbojet in accordance with claim 1, wherein said protection device is mounted to said wall via a plurality of pins, and said protective screen is mounted to said protection device via said plurality of pins.
5179832 | January 19, 1993 | Barcza et al. |
5396761 | March 14, 1995 | Woltmann et al. |
5396763 | March 14, 1995 | Mayer et al. |
6112516 | September 5, 2000 | Beule et al. |
6463739 | October 15, 2002 | Mueller et al. |
7467518 | December 23, 2008 | Vermeersch |
20020189259 | December 19, 2002 | Laing et al. |
0 744 543 | November 1996 | EP |
1 132 687 | September 2001 | EP |
1 364 192 | June 1964 | FR |
2 689 211 | October 1993 | FR |
2 770 284 | April 1999 | FR |
Type: Grant
Filed: Jul 7, 2005
Date of Patent: Oct 13, 2009
Patent Publication Number: 20060016192
Assignee: SNECMA (Paris)
Inventors: Jacques Marcel Arthur Bunel (Fresnes), Jacques André Michel Roche (Lisses), Alain Pierre Page (Montgeron)
Primary Examiner: Michael Cuff
Assistant Examiner: Gerald L Sung
Attorney: Oblon, Spivak, McClelland, Maier & Neustadt, L.L.P.
Application Number: 11/175,191
International Classification: F02K 3/10 (20060101);